The internet offers companies many opportunities to implement new business models, in short called e-Business, and to reinforce their competitiveness in the market. Despite the great interest and demand shown towards e-Business, the number of successful applications is quite few. This study suggests a framework to monitor and appraise the success of a particular e-Business operation, e-Marketplaces. To achieve this, we propose a measure, namely the e-Marketplace success index (e-MSI) to quantify the performance of e-Marketplaces. e-MSI can be effectively employed for benchmarking among digital marketplaces whether they are competing or not. More importantly, the factors shaping e-MSI are also educative - the weaknesses and strengths of e-Marketplaces with respect to key success dimensions come right to the fore. We believe that e-Marketplaces can take advantage of this information to improve their effectiveness and, at the same time, actual and/or potential companies may benefit from a uniform, objective and robust assessment of e-Marketplaces.